In the course of surgical interventions, particularly within the heart, the necessary insertion and manipulation of instruments and prostheses may apply pressure to adjacent structures which, when major blood vessels are located within those structures, may result in temporary partial or complete blockage of the vessels and an attendant risk of tissue damage.
For example during the transcatheter positioning of a replacement aortic valve, displacement of the native valve and/or the expansion of components of the replacement valve may incidentally apply pressure to adjacent cardiac wall tissue and thus to the vessels associated with that tissue. In the instance of aortic valve replacement, pressure may be transmitted to the left anterior descending (LAD) branch of the left coronary artery and in particular to the first septal branch of the LAD which supplies the anterior and superior critical portion of the interventricular conduction system. The blood supply to the left anterior fascicle is narrow and the fascicle is susceptible to ischemic damage and possible conduction disturbances. Damage, if it occurs, may be transient or permanent and may not be immediately apparent.
While stents, including temporary stents and steerable deployment/retrieval systems therefor are known in the art, those stents are deployed in an occluded or partially occluded coronary artery or other vessel and rely for their utility, in part, upon expansion to a diameter greater than the diameter of the vessel and/or an occluding deposit prior to introduction of the stent, the over-expansion being necessary to increase the patency of the vessel in which the stent is to be deployed.
Accordingly, a need exists for methods and appropriate apparatus for preventing, or at least minimizing, restriction of blood flow in the vicinity of surgical interventions.